1. Field of the Invention
The inventionrelates to the automatic measuring techniques for accurately measuring the weight of commerical products of granular foodstuffs, such as beans, before transferring them to a packaging process.
2. Description of the Prior Art
Among a large number of commercial products put on the market, granular foodstuffs such as beans are frequently sold as packaged goods.
If the actual weight of the contents of one package is less than the listed weight, a question of commercial morality is raised; but if it is greater, a problem concerning cost is raised for the seller. Hence, the weight must be accurately measured before packaging.
In practice, however, it is impossible to accurately measure the goods to a set weight, and the following method has generally been used in recent years.
The objects being measured are dispersed within a suitable dispersion range, each objects is then measured and the separate measured values thus obtained by the dispersion measurement are combined and calculated in accordance with probability and statistical logic so that the combined weight becomes a "plus minimum over quantity". The objects thus measured are packaged in individual packages.
Operational control techniques using a large number of so-called "pool" and "measuring" hoppers and a microcomputer solve this problem.
The so-called "combination measuring apparatus" in accordance with the prior art will now be described in more detail, with reference to FIG. 1. An inner frame 3 is provided above a frame 2 of a combination measuring apparatus 1, and an upper frame 4 is provided above the inner frame 3. A dispersion table 7 is positioned on this upper frame 4, concentrically with a feed port 6 for the objects being measured, in such a manner that the dispersion table 7 can rock and reciprocate through a set angle. Troughs 9 are arranged in the radial direction around the dispersion table 7, on electromagnetic vibrators 8. A pool hopper 10 and a measuring hopper 12 are provided for each trough 9 in a circumferential arrangement about the upper frame 4. Each measuring hopper 12 is positioned below the corresponding pool hopper 10, and is supported by a weight detector 11 such as a load cell provided on the frame. One each of a pool hopper 10 and a measuring hopper 12 form one unit, and 14 units, for example, are positioned around the upper frame 4. The objects being measured, such as beans, are charged from the feed port 6, are dispersed by the dispersion table 7, are sequentially by the troughs 9 to each pool hopper 10 to the corresponding measuring hopper 12, and are measured by the weight detector 11. A combination of "plus minimum over quantities" from among these measuring hoppers 12 is selected by a micro-computer (not shown), and the objects being measured are charged by the frame 2 into gathering chutes 13, 14 positioned therebelow and are thereafter transferred to the subsequent packaging step.
In the measuring and discharge process described above, covers 15, 16, 16' of the pool and measuring hoppers 10 and 12 must be opened and closed. The operating mechanisms for these covers are constructed as follows. Driving devices 19 such as cam mechanisms are arranged around a motor 17 so as to face each of the pool and measuring hoppers 12, and are driven by the motor 17 via a gear mechanism 18. Push rods 20, 21, 22 move back and forth in the radial direction in response to the operation of the corresponding driving devices, thereby openig and closing cover-operating links 23, 24, 25 for the covers 15, 16, 16'.
In accordance with the logic illustrated in FIG. 1, a predetermined number, 14 for example, of pool hoppers 10 and measuring hoppers 12 must be arranged around the upper frame 4 at a predetermined spacing. This construction inevitably results in an increase in the circumferential dimensions thereof. Moreover, weight detectors 11, such as load cells, must be provided outside the measuring hoppers 12 so as to correspond thereto, so that the size of the apparatus becomes even greater, and the space required for its installation is also greater.
This also leads to an increase in the production cost, an increase in the vibration of the apparatus, and to a drop of the measuring accuracy.
In order to reduce the size of the apparatus, it is theoretically possible to position the pool and measuruing hoppers 10 and 12 closer to one another with smaller gaps between them to reduce the outer dimensions of the apparatus. However, since the driving devices 19 operating the cover-operating links 23, 24, 25 of the pool and measuruing hoppers 10, 12 are moutned on the upper frame 4 and, moreover, since the moter 17 is disposed within the driving devices 19, a reduction in the gaps between the pool and measuring hoppers 10 and 12 leads to a reduction in the gaps between the driving devices 19 and the corresponding mechanisms, so that the driving devices interfere with the motor 17. Thus, in practice such a construction is not possble.
Accordingly, when designing a practical apparatus, the size of the motor 17 has the greatest priority, the size of the driving devices 19 is then determined thereby, followed by the sizes of the pool and measuring hoppers 10, 12 and their spacing. For these reasons, this combination measuring apparatus can not be made compact.
In conjunction with the construction of the combination measuring apparatus, the space within the circle of pool and measuring hoppers 10, 12 can not be utilized sufficiently and, even if the size of the apparatus is reduced as far as possible, the driving devices 19 or the motor 17 are utilized only spottily.
Since the structure is not compact, the operating distances of the gears, links, and push rods are large, and the power required by them is also large. Wear as well as vibration are also great, and problems are likely to occur.
The flow quantity and flow process of the objects being measured are also large and the response characteristics of the combination measuring apparatus drop, thus hindering any improvement in the performance thereof.